Enum std::task::Poll
pub enum Poll<T> { Ready(T), Pending, }
Indicates whether a value is available or if the current task has been scheduled to receive a wakeup instead.
Variants
Ready(T)
Represents that a value is immediately ready.
Tuple Fields of Ready
0: T
Pending
Represents that a value is not ready yet.
When a function returns Pending
, the function must also ensure that the current task is scheduled to be awoken when progress can be made.
Implementations
impl<T> Poll<T>
Maps a Poll<T>
to Poll<U>
by applying a function to a contained value.
Examples
Converts a Poll<
String
>
into an Poll<
usize
>
, consuming the original:
let poll_some_string = Poll::Ready(String::from("Hello, World!")); // `Poll::map` takes self *by value*, consuming `poll_some_string` let poll_some_len = poll_some_string.map(|s| s.len()); assert_eq!(poll_some_len, Poll::Ready(13));
pub const fn is_ready(&self) -> bool
Returns true
if the poll is a Poll::Ready
value.
Examples
let x: Poll<u32> = Poll::Ready(2); assert_eq!(x.is_ready(), true); let x: Poll<u32> = Poll::Pending; assert_eq!(x.is_ready(), false);
pub const fn is_pending(&self) -> bool
Returns true
if the poll is a Pending
value.
Examples
let x: Poll<u32> = Poll::Ready(2); assert_eq!(x.is_pending(), false); let x: Poll<u32> = Poll::Pending; assert_eq!(x.is_pending(), true);
impl<T, E> Poll<Result<T, E>>
Maps a Poll<Result<T, E>>
to Poll<Result<U, E>>
by applying a function to a contained Poll::Ready(Ok)
value, leaving all other variants untouched.
This function can be used to compose the results of two functions.
Examples
let res: Poll<Result<u8, _>> = Poll::Ready("12".parse()); let squared = res.map_ok(|n| n * n); assert_eq!(squared, Poll::Ready(Ok(144)));
Maps a Poll::Ready<Result<T, E>>
to Poll::Ready<Result<T, F>>
by applying a function to a contained Poll::Ready(Err)
value, leaving all other variants untouched.
This function can be used to pass through a successful result while handling an error.
Examples
let res: Poll<Result<u8, _>> = Poll::Ready("oops".parse()); let res = res.map_err(|_| 0_u8); assert_eq!(res, Poll::Ready(Err(0)));
impl<T, E> Poll<Option<Result<T, E>>>
Maps a Poll<Option<Result<T, E>>>
to Poll<Option<Result<U, E>>>
by applying a function to a contained Poll::Ready(Some(Ok))
value, leaving all other variants untouched.
This function can be used to compose the results of two functions.
Examples
let res: Poll<Option<Result<u8, _>>> = Poll::Ready(Some("12".parse())); let squared = res.map_ok(|n| n * n); assert_eq!(squared, Poll::Ready(Some(Ok(144))));
Maps a Poll::Ready<Option<Result<T, E>>>
to Poll::Ready<Option<Result<T, F>>>
by applying a function to a contained Poll::Ready(Some(Err))
value, leaving all other variants untouched.
This function can be used to pass through a successful result while handling an error.
Examples
let res: Poll<Option<Result<u8, _>>> = Poll::Ready(Some("oops".parse())); let res = res.map_err(|_| 0_u8); assert_eq!(res, Poll::Ready(Some(Err(0))));
Trait Implementations
pub fn clone(&self) -> Poll<T>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
impl<T> From<T> for Poll<T>
pub fn from(t: T) -> Poll<T>
Convert to a Ready
variant.
Example
assert_eq!(Poll::from(true), Poll::Ready(true));
pub fn from_residual(x: Result<Infallible, E>) -> Poll<Option<Result<T, F>>>
Constructs the type from a compatible Residual
type. Read more
pub fn from_residual(x: Result<Infallible, E>) -> Poll<Result<T, F>>
Constructs the type from a compatible Residual
type. Read more
pub fn cmp(&self, other: &Poll<T>) -> Ordering
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
fn clamp(self, min: Self, max: Self) -> Self
Restrict a value to a certain interval. Read more
pub fn eq(&self, other: &Poll<T>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
pub fn ne(&self, other: &Poll<T>) -> bool
This method tests for !=
.
impl<T> PartialOrd<Poll<T>> for Poll<T> where
T: PartialOrd<T>,
pub fn partial_cmp(&self, other: &Poll<T>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
fn gt(&self, other: &Rhs) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
fn ge(&self, other: &Rhs) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<T, E> Try for Poll<Result<T, E>>
type Output = Poll<T>
The type of the value produced by ?
when not short-circuiting.
type Residual = Result<Infallible, E>
The type of the value passed to FromResidual::from_residual
as part of ?
when short-circuiting. Read more
pub fn from_output(c: <Poll<Result<T, E>> as Try>::Output) -> Poll<Result<T, E>>
Constructs the type from its Output
type. Read more
pub fn branch(
self
) -> ControlFlow<<Poll<Result<T, E>> as Try>::Residual, <Poll<Result<T, E>> as Try>::Output>
Used in ?
to decide whether the operator should produce a value (because this returned ControlFlow::Continue
) or propagate a value back to the caller (because this returned ControlFlow::Break
). Read more
impl<T, E> Try for Poll<Option<Result<T, E>>>
type Output = Poll<Option<T>>
The type of the value produced by ?
when not short-circuiting.
type Residual = Result<Infallible, E>
The type of the value passed to FromResidual::from_residual
as part of ?
when short-circuiting. Read more
pub fn from_output(
c: <Poll<Option<Result<T, E>>> as Try>::Output
) -> Poll<Option<Result<T, E>>>
Constructs the type from its Output
type. Read more
pub fn branch(
self
) -> ControlFlow<<Poll<Option<Result<T, E>>> as Try>::Residual, <Poll<Option<Result<T, E>>> as Try>::Output>
Used in ?
to decide whether the operator should produce a value (because this returned ControlFlow::Continue
) or propagate a value back to the caller (because this returned ControlFlow::Break
). Read more
impl<T> StructuralEq for Poll<T>
impl<T> StructuralPartialEq for Poll<T>
Auto Trait Implementations
impl<T> RefUnwindSafe for Poll<T> where
T: RefUnwindSafe,
impl<T> Send for Poll<T> where
T: Send,
impl<T> Sync for Poll<T> where
T: Sync,
impl<T> Unpin for Poll<T> where
T: Unpin,
impl<T> UnwindSafe for Poll<T> where
T: UnwindSafe,
Blanket Implementations
impl<T> From<!> for T
pub fn from(t: !) -> T
Performs the conversion.
impl<T> From<T> for T
pub fn from(t: T) -> T
Performs the conversion.
pub fn into(self) -> U
Performs the conversion.
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
pub fn clone_into(&self, target: &mut T)
toowned_clone_into
#41263)recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/task/enum.Poll.html